Laser radar devices are known which calculate a travelling speed of aerosol from a spectrum, that is, a wind speed in a laser emission direction by applying a predetermined frequency shift to laser light emitted from a light source, emitting pulsed light, which is pulse-modulated, to the atmosphere via an optical antenna, receiving scattered light which is the pulsed light emitted to the atmosphere and reflected by fine liquid or solid particles (hereinafter referred to as aerosol) floating in the atmosphere and thereby returns, and performing frequency analysis on a digital signal of a signal of the received light.
There are cases where the laser radar devices described above are applied to wind turbines for wind power generation. In a wind turbine for wind power generation, in order to increase the operation rate of wind power generation, a configuration that is easily started even under a wind speed condition of a gentle wind is required. For example, Patent Literature 1 discloses a startup assist control device of a wind turbine that turns on a startup assistance current supplying system when the wind turbine is not rotating and turns off the startup assistance current supplying system when the wind turbine rotates at the speed of rotation greater than or equal to a certain speed by wind power. Furthermore, Patent Literature 1 discloses a technique that employs the wind speed as a control element in addition to the speed of rotation of the wind turbine and turns on the startup assistance current supplying system when the wind turbine is not rotating and the wind speed is greater than or equal to a startup wind speed of the wind turbine.